The 1892 RLDS edition omitted the repeated infinitival to in this passage; the 1908 RLDS edition restored it to the RLDS text. For further discussion regarding the repeated to in infinitive clauses, see under 3 Nephi 4:23. Also see under Jacob 7:2 for another instance where the 1892 RLDS edition omitted the repeated infinitival to. For further discussion of the repetition of the to in infinitival conjuncts, see under conjunctive repetition in volume 3.
Summary: Maintain the repeated infinitival to in 3 Nephi 6:4, “to prosper and to wax great” (the reading of the earliest extant text).